Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!widener!brendan
From: brendan@cs.widener.edu (Brendan Kehoe)
Newsgroups: comp.lang.c
Subject: re-sizing a 2-dim array
Message-ID: <MQR+3BK@cs.widener.edu>
Date: 16 May 91 18:14:55 GMT
Organization: Widener CS Dept
Lines: 36


 I have a two-dimensional array, that I need to dynamically allocate
at run-time. It's declared as:
	LINE **contents;

 I need to be able to read in any arbitrarily large list (n lines) into
this array. I don't know how long the list is. (The example in the
FAQ, of allocating n rows, can't be used in this case, since I've no
idea how many rows could be in it to start with.)

 I was thinking of setting a limit of, say, 4096 or 8192 on it to
begin with (declare it as
	LINE **contents = (LINE **) malloc (sizeof(LINE *) * 4096);
for example). Then, when it read line 4097 (going outside the bounds
of the current set), it'd bump the whole thing up to 8192 (or some
increment), as so: 
	LINE **new_contents = (LINE **) malloc (sizeof(LINE *) * 8192);
and then do something like:

	bcopy((char *)contents, (char *)new_contents, sizeof(LINE *) * 4096);
	free(contents);
	contents = new_contents;

to move the old set of pointers over to the new one.

 Is this a reasonable way to do it? Is there a better way?

 Thanks..

Brendan

-- 
     Brendan Kehoe - Widener Sun Network Manager - brendan@cs.widener.edu
  Widener University in Chester, PA                A Bloody Sun-Dec War Zone
 "Visualize a dream; look for it in the present tense -- a greater calm than
   before.  If you persist in your efforts, you can achieve...dream control."